Author: DW Layton

Alert: Winter cold spells can lead to extra dry skin

The onset of cooler, dry outdoor air of the winter months produces increased indoor drying stresses on your skin. As a result, people use moisturizing lotions and creams as well as room humidifiers to minimize the formation of dry skin. However, when a major cold front or a “Polar Vortex” event occurs, it can really disrupt your skin care!

Why do winter cold fronts increase the risk of dry skin?

Most of the news surrounding a winter cold front will focus on reduced temperatures and wind-chill factors, yet the indoor environment will be impacted too–including your skin care. Why would this be? First of all, as the cold front hits, the water vapor content of outdoor air can drop dramatically along with temperature. These changes result in lower indoor humidities as the dry air seeps into much warmer houses. Second, to reduce your heating bill you may want to turn the thermostat down a bit (this is a good thing), but the lower indoor temperature and humidity will actually increase the drying stresses on your skin. Third, you can’t sense the magnitude of these dermal drying stresses, and consequently, you may not think about the need to hydrate skin. The final, surprising result for many people, including those with aging skin, is the formation of unexpected dry, rough, or flaky skin!

How can you adapt your skin care to weather events?

To help address the dermal indoor stresses brought on by a major winter cold system, think about the potential increases in the indoor drying stresses on your skin and plan on using extra skin moisturizers as well as a room humidifier to counteract the dermal stresses.

Dermidia also offers the DSI Sense sensor device plus smartphone app that constantly tracks the Dry Skin Index, which is a measure of indoor drying stresses caused by changes in temperature and relative humidity. With the DSI Sense, you won’t be caught off-guard by weather events that alter indoor conditions impacting your skin. This feature may be particularly valuable to people whose skin is prone to seasonal dryness.


  • When a major cold front hits, we think of the temperatures and wind chill factors because they make the headlines. Nevertheless, the indoor environment is impacted as well–including our skin care!
  • Anticipate the changes in the indoor drying stresses on your skin as the cold front passes, and compensate by applying moisturizing creams and lotions to areas of your skin that are prone to dryness. Room humidifiers are also useful because they can help hydrate skin when moisturizers alone may not be enough.
  • Consider getting a DSI Sense to monitor skin stressors so that you can proactively manage your skin care in response to changes in the weather.
Skin Sim app simulates seasonal drying stresses on skin at a reference house

Use the Skin Sim app to guide your seasonal skin care

The Skin Sim app simulates seasonal changes in drying stresses on skin at a reference house in your community. It uses an indoor air model along with historic climatic data from NASA to reconstruct these stresses.

The app presents two diagnostics for evaluating these stresses. The first is the Dermal Hydration Deficit. The hydration deficit represents the difference between the skin’s water content at an optimum value of 60% relative humidity and the content at an indoor humidity below 60%. The Dry Skin Index is based on a thermodynamic property of water vapor. I is calculate from indoor temperature and humidity.

How can Skin Sim help you improve your skin care?

A motivating force behind Dermidia is the recognition that 1) as we age our skin becomes more susceptible to indoor drying stresses, and 2) these stresses change seasonally, but we can’t sense them directly. Therefore, we need tools to guide our skin-care practices over the course of a year.

One such tool we developed is the app Skin Sim, which is available from Google Play and iOS App Store.

The adjacent screen shot depicts the simulation results from the app for a location that has a large number of days in which the Dry Skin Index is above 5. Perhaps the biggest surprise is how the drying stresses increased rapidly in the early fall after the humid summer months. This is apt to be a time when people begin experiencing dry skin without necessarily knowing the cause.

Conversely, stresses begin to let up in late Spring, which means that your skin-care should change as well.

You can become more knowledgeable about the seasonal drying stresses impacting your skin care by using the Skin Sim app.

Skin Sim by Dermidia simulates the Dry Skin Index

Discover patterns of dermal drying stresses that matter to you. Prepare and respond accordingly!

Dave Layton, Owner, Dermalapps LLC

Action items

It is quite easy to use the Skin Sim app–download from one of the app stores and type in your location.

  • Pay particular attention to the number of days above DSI levels of 5 and 6, as these elevated levels increase the risk of dry skin formation.
  • Identify times of year in which the Dry Skin Index is rapidly increasing or decreasing.
  • Consider how to compensate for these changing stresses by applying moisturizing lotions/creams to areas of skin prone to dryness.
  • Don’t forget about room humidifiers as another way to reduce drying stresses when indoor humidities are low.

For more personal, timely and relevant information on the drying stresses impacting your skin, consider getting the DSI Sense. This sensor constantly tracks the dermal stresses in your residence so that you can adjust your skin-care practices accordingly. Avoid the seasonal surprises that other face. Compensate for the increasing susceptibilities of aging skin to indoor drying conditions by the proactive use of moisturizers and room humidifiers.

What levels of the Dry Skin Index initiate dry-skin formation?

A fundamental issue impacting our personal skin care is the inability to sense the magnitude of drying stresses on skin. This really inhibits the timely and effective use of skin moisturizers and/or humidifier. The Dry Skin Index (DSI) measures these stresses, which are conveniently monitored using Dermidia’s DSI Sense + smartphone app. But what levels of the Dry Skin Index might trigger dry-skin formation?

The Dry Skin Index is broken down into five stress categories ranging from very low to very high. Previously we identified the optimum relative humidity associated hydrated skin, but not the DSI levels at which people should begin to hydrate skin. Fortunately, data derived from a study by Jin et al. (2021) allows us to identity key threshold levels.

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A humidifier supports better skin care

Use a humidifier to fight winter dry skin!

Millions of people use humidifiers to combat seasonal dry air and its impact on skin (e.g., “winter dry skin”). However, it may not always be clear how well they work and whether they really can support better skin care. These are important concerns, so I decided to conduct a simple test using a small room humidifier in my home office.

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Consider moisturizers with ceramides for aging skin

Healthy, hydrated skin does not show signs of dryness such as dry spots or skin flakes. Skin hydration depends on the barrier function of the skin’s outer layer (stratum corneum). Lipids (fats) in this outer layer help control the loss of water from the skin. Ceramides are a key component of skin lipids. They are also used as an active ingredient in various moisturizing lotions and creams.

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Home office

How working at home supports your skin care

Efforts to control the Covid-19 epidemic included lockdowns that forced millions of people to work at home in addition to those previously doing so. If you are now working from home, then you have probably already considered the many pros and cons of this arrangement. One of the “collateral” benefits you might not have considered is that working at home can actually support better skin care! Although this assertion may not seem obvious, there are at least 4 reasons why you should enjoy healthier skin at home, as compared to working elsewhere:

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When should you turn on a humidifier to hydrate your skin?

Each year people in the USA conduct Internet searches for the term “humidifier”. These searches are seasonal in nature and coincide with the drying trends in the weather that impact indoor air. Internet searches for “humidifier” are also seasonally correlated with searches for “dry skin”, which makes sense because people use humidifiers to deal with dry skin and other conditions related to dry indoor air.

Depending on your situation, you can decide to turn on your humidifier when:

  1.  you start experiencing dry skin,
  2. the indoor heating season starts in early fall,
  3. the relative humidity is below a target range of 40 to 60%, or
  4. the Dry Skin Index exceeds 6.

Humidifier use trigger: dry-skin symptoms

One option for deciding when to set up your room or portable humidifier is the condition of your skin. Specifically, does your skin exhibit drying symptoms such as dandruff, flakes, itchiness, or roughness? As a first course of action, it may actually be easier to apply a skin moisturizer to dry areas of your skin instead of running a humidifier. However, as indoor air gradually becomes drier into the fall, moisturizer therapy alone may not completely alleviate your symptoms. In this situation, consider using a humidifier in your bedroom when you sleep. This is a reasonable “first-use” of a humidifier. Nevertheless, if dry-skin conditions persist, a room humidifier together with the selective application of moisturizing lotions and creams constitutes a flexible treatment strategy.

Humidifier use trigger: start of heating season

If you don’t want to wait for dry-skin symptoms to develop before using a humidifier, then an easy-to-remember trigger is the start of the heating season. The cooler outdoor air that prompts the use of indoor heating also contains lower levels of water vapor. As the cool, dry air enters a warmer residence the relative humidity drops because the warm air can hold a lot more water vapor. Lower indoor temperatures and humidities put increased drying stresses on skin–causing seasonal dry skin.

For many parts of the USA, October marks the beginning of the heating season, which makes it a good month to get your humidifier ready and to check whether you have moisturizers ready for use too.

Humidifier use trigger: target relative humidity

Research has shown that the optimum relative humidity for healthy skin is about 60%. As the relative humidity decreases below that level, your skin begins to dehydrate, and therefore the need for remedial rehydration measures increases, including the application of moisturizers to impacted skin and/or the operation of a room humidifier.

There is no standard “trigger” level of relative humidity for starting up a humidifier, but 40% RH seems to be a good default level–and here’s why. Relative humidities just below 60% are probably best handled by simply applying a moisturizer to the areas of your skin that are prone to dryness. Below 40% RH, the extra hydration provided by a humidifier can help ameliorate the external drying stresses over your entire skin surface.

Humidifier use trigger: Dry Skin Index above 6

An alternative “trigger” is to consider a room humidifier when the Dry Skin Index (DSI) exceeds a value of 6. The risk of dry-skin formation generally starts when the DSI level is between 4 and 5, depending on how a person’s skin responds to drying stresses. Also, older people are likely to be more susceptible to dry skin formation due to biochemical changes in the skin’s barrier function with age. At moderate levels of the DSI, skin moisturizers are usually the most convenient way of keeping skin hydrated, but at high levels (DSI 6 +), a room humidifier becomes a useful tool in keeping your skin hydrated. If you work from home, you have more flexibility to use a humidifier in selected rooms that you use.

Humidifier triggers: some pros and cons

The “best” trigger for you is the one that is most likely to get you to start up a humidifier! Perhaps the most “persuasive” trigger is the development of dry-skin symptoms. However, waiting for symptoms to occur delays the timely treatment of skin dehydration.

Alternatively, the start of the heating season can serve as a reminder that the time is at hand to start up a humidifier—prior to the manifestation of dry-skin symptoms. If that trigger proves problematic (will you really remember to get the humidifier out?), then monitoring indoor relative humidity constitutes another option. Nevertheless, one pitfall here is that inexpensive humidity sensors can give inaccurate readings of relative humidity, which means that you could be basing your skin-care decisions on erroneous information.

Ultimately, your awareness of the relationship between seasonal drying stresses on your skin and effective treatment options–including a room humidifier, constitutes the best motivational “trigger” for pursuing timely skin care.

Treat dry skin to reduce proinflammatory cytokines contributing to age-related diseases

Keeping your skin hydrated as you age is necessary to maintain your skin’s barrier function and inhibit the formation of dry skin. Research now indicates that a collateral benefit of hydrating skin care is a reduction in proinflammatory cytokines circulating in blood. These agents in blood plasma have been associated with inflammaging, which is low level, subclinical inflammation prevalent in aging populations.

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